Tandem fan assembly with airflow-straightening heat exchanger

ABSTRACT

A tandem fan system with an airflow-straightening heat exchanger removes heat from an airflow while providing optimal airflow pressure. The tandem fan system includes a first fan assembly and a second fan assembly, wherein each fan assembly has an inlet face and an outlet face, and includes at least one fan configured to propel a flow of air from the inlet face to the outlet face. The tandem fan system also includes a heat exchanger coupled between the first and second fan assemblies, wherein the heat exchanger includes at least one fin array and one or more heat pipes. The fin array and heat pipe combination is configured to draw heat from a flow of air that flows through the heat exchanger, and to straighten the flow of air so that the flow is perpendicular to the inlet face of the second fan assembly.

BACKGROUND

1. Field

The disclosed embodiments are related to cooling mechanisms. Morespecifically, the disclosed embodiments are related to a fan assemblies.

2. Related Art

Many large corporations are increasing their use of data centers as theydevelop new ways of using information systems to optimize their businessoperations. Furthermore, the increasing popularity of the Internet andcloud-based computing is fueling demand for ever-larger data centersthat can store and process enormous volumes of information.Consequently, in an effort to increase the performance of servers indata centers, system designers are equipping servers with more devices(i.e., processors, networking devices, peripheral devices, powerconverters, and other devices). As the number of devices increases, theheat produced by the devices can cause the internal temperature of aserver to rise to a point where the devices can be damaged or canexperience significantly shortened lifespans. To mitigate theseproblems, servers are typically equipped with one or more fans to forcea flow of air through the server to remove internal heat from theserver.

Some servers produce so much heat that the flow of air produced by fansin traditional arrangements is insufficient to control the internaltemperature of the server, some servers include multi-fan assembliesthat are configured to generate a high-volume airflow using two fantrays in tandem. For example, FIG. 1A illustrates a typical tandem fanassembly 100, which includes fan trays 102-104 oriented in series andseparated by a distance 106. The fans in fan trays 102 and 104 drive aflow of air in direction 108, so that air that exits an outlet face offan tray 102 enters an inlet face of fan tray 104.

Although they increase overall airflow, fan assemblies (such as tandemfan assembly 100) may not produce an optimal airflow pattern because theairflow that exits the outlet face of fan tray 102 is not perpendicularto the inlet face of fan tray 104. More specifically, the airflow exitsthe outlet face of fan tray 102 in a turbulent twisting motion (i.e.,with an approximately helical velocity vector). Thus, instead of hittingthe fan blades of fan tray 104 in the orientation for which the fans infan tray were optimized (i.e., perpendicular to the face of fan tray104), the airflow hits the fan blades at suboptimal angles.Consequently, the combination of fan tray 102 and fan tray 104 mayproduce slightly more airflow pressure than a single fan tray, but doesnot produce twice the airflow pressure of a single fan tray.

In an effort to increase the efficiency of fan assemblies such as theillustrated fan assembly, designers have included airflow-straighteningelements between the fan trays. Airflow-straightening elements canstraighten and re-orient the turbulent flow of air as it passes betweenthe fan trays to ensure that the air hits the blades of fan tray 104 atan angle closer to the optimal angle. For example, FIG. 1B illustratesan exemplary tandem fan assembly 110 with an airflow-straightener 116.Tandem fan assembly 110 includes fan trays 112 and 114 oriented inseries, and includes an airflow-straightener 116 between fan trays112-114. The fans in fan trays 112 and 114 drive a flow of air indirection 118, such that air that exits an outlet face of fan tray 112flows through airflow-straightener 116 before entering an inlet face offan tray 114. Airflow-straightener 116 can include a set of fins forstraightening the flow of air. For example, FIG. 1C presents ahoneycomb-shaped fin 122 in an airflow straightener 120.

Unfortunately, because the fans can consume a significant portion of aserver's overall power, and because a limited number of fan assembliescan be mounted on a given server, many servers cannot be keptsufficiently cool even using these existing multi-fan assemblies.

SUMMARY

The described embodiments provide a tandem fan system that removes heatfrom an airflow while also providing improved airflow pressure. Thetandem fan system includes a first fan assembly and a second fanassembly. Each of these fan assemblies has an inlet face and an outletface, and at least one fan coupled between the inlet face and the outletface. In the described embodiments, the fans are configured to draw aflow of air into the inlet face and propel the flow of air out of theoutlet face. The tandem fan system also includes a heat exchangercoupled between the first fan assembly and the second fan assembly.

In the described embodiments, the heat exchanger includes a first facecoupled to the outlet face of the first fan assembly, and a second facecoupled to the inlet face of the second fan assembly. The heat exchangerfurther includes at least one fin array coupled between the first faceand the second face that is configured to straighten a flow of air thatflows through the heat exchanger from the outlet face of the first fanassembly to the inlet face of the second fan assembly. The heatexchanger also includes one or more heat pipes coupled between the firstface and the second face configured to draw heat from the flow of airthat flows through the heat exchanger.

In some embodiments, the at least one fin array includes a corrugatedfin.

In some embodiments, the one or more heat pipes are interdigitated withthe at least one fin array.

In some embodiments, a heat pipe is mechanically coupled to fins of atleast one neighboring fin array.

In some embodiments, the heat exchanger also includes an inlet headercoupled to one end of the one or more heat pipes, and an outlet headercoupled to an opposing end of the one or more heat pipes.

In some embodiments, the heat exchanger also includes a mechanical pumpconfigured to propel a flow of a liquid or a gas in the heat pipe fromthe inlet header to the outlet header.

In some embodiments, the liquid or gas is selected from the groupconsisting of: air; water; a liquid coolant in an R133 group ofcoolants; and a liquid coolant in an R134 group of coolants.

In some embodiments, a heat pipe includes a set of internal fins.

In some embodiments, the set of internal fins includes at least onecorrugated fin.

In some embodiments, a heat pipe has a depth of between 20 mm and 40 mm,which spans the first face and the second face of the heat exchanger.

In some embodiments, two neighboring fins in the at least one fin arrayhave a separation distance of between 0.5 mm and 2 mm.

In some embodiments, a fin in the at least one fin array has a length ofbetween 10 mm and 20 mm.

In some embodiments, a fin in the at least one fin array has a depthbetween 20 mm and 40 mm, which spans the first face and the second faceof the heat exchanger.

In some embodiments, a fan assembly has a depth equal to 50 mm.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A illustrates a typical tandem fan assembly.

FIG. 1B illustrates a typical tandem fan assembly with anairflow-straightener.

FIG. 1C illustrates a honeycomb-shaped fin in an airflow-straightener.

FIG. 2A illustrates elements of a tandem fan assembly in accordance withthe described embodiments.

FIG. 2B illustrates a cross-section of a portion of a heat exchanger inaccordance with the described embodiments.

FIG. 3 illustrates an assembled tandem fan assembly in accordance withthe described embodiments.

FIG. 4 illustrates a chassis that includes a tandem fan assembly inaccordance with the described embodiments.

In the figures, like reference numerals refer to the same figureelements.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use the embodiments, and is provided in the contextof a particular application and its requirements. Various modificationsto the disclosed embodiments will be readily apparent to those skilledin the art, and the general principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the present disclosure. Thus, the present invention is notlimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein.

Air-Cooling Tandem Fan System

The described embodiments provide a fan assembly that uses two or morefan trays to generate an airflow that can be used to cool devices in aserver, a computer system, or in another device. In the describedembodiments, the tandem fan assembly includes at least one heatexchanger mounted between the fan trays. In these embodiments, the heatexchanger includes one or more mechanisms for straightening and coolingan airflow that is driven through the fan assembly.

FIG. 2A illustrates elements of a tandem fan assembly 200 in accordancewith the described embodiments. Tandem fan assembly 200 includes two fantrays (i.e., fan trays 202 and 206) coupled in series, and a heatexchanger 210 coupled between fan trays 202 and 206. Each fan tray hasan inlet face and an outlet face. The fans of a given fan tray (e.g.,fans 203-204 of fan tray 202) draw an airflow into the inlet face andpropel an airflow out of the outlet face.

In the described embodiments, one face of heat exchanger 210 is coupledto the outlet face of fan tray 202, and an opposing face of heatexchanger 210 is coupled to the inlet face of fan tray 206. Duringoperation, fans 203-204 are configured to propel an airflow in adirection 224 so that the airflow passes through heat exchanger 210. Inaddition, fans 207-208 of fan tray 206 are configured to draw an airflowfrom heat exchanger 210 in direction 224.

In some embodiments, heat exchanger 210 includes a set of fin arraysthat includes at least one fin array (e.g., fin array 212), a set ofheat pipes that includes at least one heat pipe (e.g., heat pipe 214),and headers 216-218. The set of fin arrays can be mechanically coupledto the set of heat pipes to form a fin assembly, in which the set of finarrays is interdigitated with the set of heat pipes in an alternatingsequence of fin arrays and heat pipes along an axis of heat exchanger210.

Moreover, the fin arrays and the heat pipes of heat exchanger 210 arelocated in a common space (i.e., within a common layer). Thisconfiguration enables heat exchanger 210 to reduce the heat in theairflow and to provide an airflow oriented in a predetermined directionwith a lower drop in airflow pressure than is possible by a system thatis implemented using a separate heat exchanger and airflow-straightener(i.e., a physically separate heat exchanger and airflow-straightener).

Fin array 212 is configured to straighten the direction of airflow thatflows from fan tray 202 to fan tray 206 so that the airflow arrives atfan tray 206 in a predetermined orientation with respect to the inletface of fan tray 206. For example, in some embodiments, fin array 212 isconfigured to straighten the direction of airflow and orient the airflowso that the airflow arrives at the inlet face of fan tray 206 orientedperpendicularly to the inlet face of fan tray 206. Furthermore, the finsof a fin array are thermally coupled (i.e., mechanically coupled usingone or more heat-transferring coupling mechanisms) to neighboring heatpipes, to increase the surface area of the heat exchanger that capturesheat from the airflow. More specifically, as the fans of tandem fanassembly 200 propel the airflow through heat exchanger 210, the fins ofheat exchanger 210 capture heat from the airflow while straightening theairflow, and transfer the captured heat to the neighboring heat pipes.

Heat pipe 214 is configured to capture heat from the airflow thattravels from fan tray 202 to fan tray 206, and to transfer the heatthrough a header (e.g., header 218) on heat exchanger 210 to anenvironment outside tandem fan assembly 200. Each heat pipe 214 is anoval-shaped tube with a cavity filled with a heat-transferring gas orliquid. As shown in FIG. 2A, headers 216 and 218 can be coupled toopposing ends of each heat pipe, and configured so that theheat-transferring fluid flows from header 216, through the heat pipe,and to header 218. In the described embodiments, one or more elements ofheat exchanger 210 (e.g., the fins of a fin array, a heat tube, and/or aheader) are formed using a heat-conducting material such as copper,aluminum, a ceramic material, or another material.

In some embodiments, a mechanical pump (e.g., pump 406 in FIG. 4) candrive a heat-transferring fluid into header 216 and draw theheat-transferring fluid from header 218. More specifically, themechanical pump can drive a heat-transferring fluid into at least one ofthe two ends of header 216 (e.g., via inlet 220). Then, theheat-transferring fluid is driven through the one or more heat pipes,absorbing heat that is captured from the airflow by the fin assembliesof heat exchanger 210. The heat-transferring fluid is then driven out ofheat exchanger 210 via at least one of the two ends of header 218 (e.g.,via outlet 222).

FIG. 2B illustrates a cross-section of a portion of heat exchanger 210in accordance with the described embodiments. The heat exchangercross-section includes two tubes with oval cross-sections (i.e., ovaltubes 230-232), and a corrugated fin 234 coupled between oval tube 230and oval tube 232. Corrugated fin 234 corresponds to fin array 212 ofFIG. 2A, such that corrugated fin 234 includes a series of folds thatform alternating parallel ridges and furrows. Also, oval tubes 230-232correspond to a heat pipe of FIG. 2A (e.g., heat pipe 214).

The configurations and dimensions of a heat exchanger can vary fordifferent tandem fan assemblies. For example, corrugated fin 234 canhave a pitch 242 (i.e., a separation distance between consecutive foldsof the corrugated fin) that can vary from 0.5 mm to 2 mm. Furthermore,the depth of a corrugated fin and/or the depth of an oval tube (i.e.,fin depth 246 and tube depth 248) can each vary from 20 mm to 40 mm. Thefin length 244 (i.e., the separation distance between two neighboringoval tubes) can vary from 10 mm to 20 mm. Although we describeparticular ranges of sizes and dimensions for the elements shown in FIG.2B, in alternative embodiments other sizes and dimensions can be used.

Oval tubes 230-232 can be assembled using a configuration that increasestheir efficiency for capturing heat from the airflow through heatexchanger 210. For example, oval tubes 230-232 include a set of internalfins (e.g., fins 236-237) that guide the direction of heat-transferringfluid that flows within oval tubes 230-232. These internal fins cancause the heat-transferring fluid to flow more efficiently through ovaltube 230 (e.g., by minimizing turbulence in the flow), thereby allowingheat-transferring fluid that has a lower temperature to enter oval tube230 at a higher rate. The more efficient flow can lower the operatingtemperature of oval tube 230, which in turn increases the ability foroval tube 230 to capture heat from the airflow through heat exchanger210.

In some embodiments, the internal fins can include one or morecorrugated fins (i.e., corrugated fins 236-237) that have an orientationthat is parallel to the side walls of the enclosing oval tube (i.e.,perpendicular to a face of the heat exchanger). In alternativeembodiments, the internal fins can include an array of individual fins(not shown) that have an orientation that is perpendicular to the sidewalls of the enclosing oval tube (i.e., parallel to a face of the heatexchanger).

In some embodiments, the internal fins of oval tube 230 can beconfigured to mix the heat-transferring fluid as it flows through ovaltube 230, thereby enabling the heat-transferring fluid to remove heatfrom an ambient airflow more efficiently. For example, the pattern of acorrugated fin can vary at different portions of oval tube 230 so thatheat-transferring fluid which is in thermal contact with oval tube 230at one portion of oval tube 230 is forced toward the center of oval tube230 at a different portion of oval tube 230. Similarly,heat-transferring fluid which is at the center of oval tube 230 at oneportion of oval tube 230 is forced toward the wall of oval tube 230 at adifferent portion of oval tube 230.

FIG. 3 illustrates an assembled tandem fan assembly 300 in accordancewith the described embodiments. Tandem fan assembly 300 includes fantrays 302-304, and a heat exchanger 306. A typical fan tray can includetwo fans with a fan diameter 310 that is equal to 150 mm.Correspondingly, typical dimensions of fan trays 302-304 and heatexchanger 306 can include a height 312 equal to 200 mm, a width 314equal to 400 mm, and a depth 316 equal to 50 mm.

Moreover, fan trays 302 and 304 can be mechanically coupled to opposingsides of heat exchanger 306. For example, the outflow face of fan tray302 can be coupled to a face of heat exchanger 306 by using one or morebinding techniques known in the art, such as brazing, gluing, bindingwith epoxy, welding, or mechanically attaching (e.g., bolting, screwing,etc.). This configuration ensures that a gap does not separate a fantray from heat exchanger 306, so that the airflow that exits the outflowface of fan tray 302 flows directly to the inflow face of fan tray 304.

Although we describe particular dimensions and configurations for theillustrated embodiments, alternative embodiments are of different sizesand arrangements. For example, the dimensions of fan trays 302-304 andheat exchanger 306 can vary depending on fan diameter 310, the number offans per fan tray, and a minimum spacing required between two fans on afan tray or between an edge of a fan and the perimeter of the fan tray.In some embodiments, fan diameter 310 can vary from 100 mm to 200 mm.Further, a fan tray with two fans and a minimum spacing of 25 mm canhave a minimum height 312 that varies from 150 mm to 250 mm, and canhave a minimum width 314 that varies from 275 mm to 475 mm.

Although we show fan trays 302 and 304 directly coupled to heatexchanger 306, in alternative embodiments, a standoff (not shown) can beused to attach a fan tray to heat exchanger 306, thereby separating fantrays 302-304 from heat exchanger 306 by a predetermined distance. Morespecifically, the outflow face of fan tray 302 can be oriented apredetermined distance from a first side of heat exchanger 306, and theinflow face of fan tray 304 can be oriented a predetermined distancefrom an opposing side of heat exchanger 306. In this configuration, theseparation distance between the outflow face of fan tray 302 and theinflow face of fan tray 304 can vary from 25 mm to 50 mm. Further, depth318 for heat exchanger 306 can vary from 20 to 40 mm, such that depth318 is not greater than the separation distance between fan trays 302and 304. In these embodiments, the standoff can be configured so that agap does not separate one of the fan trays from a standoff or a standofffrom heat exchanger 306 in order to guarantee that the airflow thatexits the outflow face of fan tray 302 flows directly to the inflow faceof fan tray 304.

FIG. 4 illustrates a chassis that includes a tandem fan assembly inaccordance with the described embodiments. In some embodiments, chassis400 can be a chassis for a computer system, which provides a housing fora variety of heat-producing computer components such as one or morepower supplies, processing elements (e.g., a microprocessor, anexpansion card, etc.), cards (e.g., network cards), and/or memorystorage devices. In other embodiments, chassis 400 can be mounted in acabinet that houses a number of similar chassis and/or other computingdevices, such as rack-mount servers.

Chassis 400 includes tandem fan assemblies 402-404, a pump 406, a heatsink 407, and channels 408-409. During operation, pump 406 drives aliquid or a gas through channels 408-409 in fluid-flow directions410-411, respectively. Pump 406 can be thermally coupled to heat sink407 to transfer heat from the liquid or gas to an environment that isexternal to chassis 400. In some embodiments, pump 406 can drive acooled liquid that is obtained from a source external to chassis 400 toincrease the temperature gradient between the liquid in the heatexchanger and the airflow that is being cooled by the heat exchanger.

In some embodiments, pump 406 drives the fluid through tandem fanassembly 402 and tandem fan assembly 404 in series. Specifically,channel 409 is coupled to an outlet port for a header on tandem fanassembly 402, and is coupled to an inlet port for a header on tandem fanassembly 404, thereby circulating a fluid flow in direction 411. Inother embodiments, pump 406 drives the fluid through tandem fan assembly402 and tandem fan assembly 404 in parallel (not shown).

Tandem fan assembly 402 can be configured to propel airflow in airflowdirection 412 into chassis 400. Unlike a typical fan assembly, the heatexchanger of tandem fan assembly 402 decreases the heat load that istransferred from the external environment and from the motors of tandemfan assembly 402 into chassis 400. Furthermore, tandem fan assembly 404can be configured to propel airflow from chassis 400 in airflowdirection 414 into an external environment (e.g., a server room). Unlikea typical fan assembly, the heat exchanger of tandem fan assembly 404decreases the heat load that is transferred from the interior of chassis400 into the external environment.

Note that chassis 400 can include more or fewer tandem fan assembliesand channels oriented in a variety of configurations to achieve adesired airflow pressure and/or volume of cooled airflow that traversesheat-producing components (not shown, but including processors,peripheral devices, cards, interface devices, networking devices, etc.)in chassis 400. For example, additional tandem fan assemblies can beconfigured to propel cooled airflow into chassis 400, and/or additionalfan assemblies can be configured to propel cooled airflow from theinterior of chassis 400 to the external environment. Furthermore, a setof channels can be configured to drive a fluid flow through one group oftandem fan assemblies in series while driving other fluid flows throughother tandem fan assemblies in parallel.

The foregoing descriptions of various embodiments have been presentedonly for purposes of illustration and description. They are not intendedto be exhaustive or to limit the present invention to the formsdisclosed. Accordingly, many modifications and variations will beapparent to practitioners skilled in the art. Additionally, the abovedisclosure is not intended to limit the present invention.

1. A tandem fan system, comprising: a first fan assembly and a secondfan assembly, wherein each fan assembly has an inlet face and an outletface and at least one fan coupled between the inlet face and the outletface, wherein the at least one fan is configured to propel a flow of airfrom the inlet face to the outlet face; and a heat exchanger coupledbetween the first fan assembly and the second fan assembly, comprising:a first face coupled to the outlet face of the first fan assembly and asecond face coupled to the inlet face of the second fan assembly; atleast one fin array coupled between the first face and the second face,wherein the fin array is configured to straighten a flow of air thatflows through the heat exchanger from the outlet face of the first fanassembly to the inlet face of the second fan assembly so that the flowis oriented in a predetermined direction with respect to the inlet faceof the second fan assembly; and one or more heat pipes coupled to the atleast one fin array between the first face and the second face, whereinthe heat pipes are configured to draw heat from the flow of air thatflows through the heat exchanger.
 2. The tandem fan system of claim 1,wherein the at least one fin array includes a corrugated fin.
 3. Thetandem fan system of claim 1, wherein the one or more heat pipes areinterdigitated with the at least one fin array.
 4. The tandem fan systemof claim 3, wherein the heat exchanger is configured to straighten theflow of air so that it is oriented in a perpendicular direction withrespect to the inlet face of the second fan assembly.
 5. The tandem fansystem of claim 1, wherein the heat exchanger further comprises: aninlet header coupled to one end of the one or more heat pipes; and anoutlet header coupled to an opposing end of the one or more heat pipes.6. The tandem fan system of claim 5, further comprising a mechanicalpump configured to propel a flow of a liquid or a gas in the heat pipefrom the inlet header to the outlet header.
 7. The tandem fan system ofclaim 6, wherein the liquid or gas is selected from the group consistingof: air; water; a liquid coolant in an R133 group of coolants; and aliquid coolant in an R134 group of coolants.
 8. The tandem fan system ofclaim 1, wherein a heat pipe comprises a set of internal fins.
 9. Thetandem fan system of claim 8, wherein the set of internal fins includesa corrugated fin.
 10. The tandem fan system of claim 1, wherein a heatpipe has a depth between 20 mm and 40 mm, which spans the first face andthe second face of the heat exchanger.
 11. The tandem fan system ofclaim 1, wherein two neighboring fins in the at least one fin array havea separation distance between 0.5 mm and 2 mm.
 12. The tandem fan systemof claim 1, wherein a fin in the at least one fin array has a lengthbetween 10 mm and 20 mm.
 13. The tandem fan system of claim 1, wherein afin in the at least one fin array has a depth between 20 mm and 40 mm,which spans the first face and the second face of the heat exchanger.14. The tandem fan system of claim 1, wherein a fan assembly has a depthequal to 50 mm.
 15. A method for cooling air using fan assemblies,wherein each fan assembly has an inlet face and an outlet face and atleast one fan coupled between the inlet face and the outlet face,wherein the at least one fan is configured to propel a flow of air fromthe inlet face to the outlet face, the method comprising: using a firstfan assembly and a second fan assembly to propel air from the outletface of the first fan assembly to the inlet face of the second fanassembly; and using a heat exchanger coupled between the first fanassembly and the second fan assembly to straighten the flow of air sothat it is oriented in a perpendicular direction with respect to theinlet face of the second fan assembly by: coupling a first face of theheat exchanger to the outlet face of the first fan assembly; coupling asecond face of the heat exchanger to the inlet face of the second fanassembly; coupling at least one fin array between the first face and thesecond face, wherein the fin array is configured to straighten a flow ofair that flows through the heat exchanger from the outlet face of thefirst fan assembly to the inlet face of the second fan assembly so thatthe flow is oriented in a predetermined direction with respect to theinlet face of the second fan assembly; and coupling one or more heatpipes to the at least one fin array between the first face and thesecond face, wherein the heat pipes are configured to draw heat from theflow of air that flows through the heat exchanger.
 16. The method ofclaim 15, wherein the at least one fin array includes a corrugated fin.17. The method of claim 15, wherein the method further comprisesconfiguring the one or more heat pipes to be interdigitated with the atleast one fin array.
 18. The method of claim 15, wherein the methodfurther comprises: coupling an inlet header to one end of the one ormore heat pipes; and coupling an outlet header to an opposing end of theone or more heat pipes.
 19. The method of claim 18, wherein the methodfurther comprises configuring a mechanical pump to propel a flow of aliquid or a gas in the heat pipe from the inlet header to the outletheader.
 20. An electronic device, comprising: a chassis; a first fanassembly and a second fan assembly coupled to the chassis, wherein eachfan assembly has an inlet face and an outlet face and at least one fancoupled between the inlet face and the outlet face, wherein the at leastone fan is configured to propel a flow of air from the inlet face to theoutlet face; and a heat exchanger coupled between the first fan assemblyand the second fan assembly, comprising: a first face coupled to theoutlet face of the first fan assembly and a second face coupled to theinlet face of the second fan assembly; at least one fin array coupledbetween the first face and the second face, wherein the fin array isconfigured to straighten a flow of air that flows through the heatexchanger from the outlet face of the first fan assembly to the inletface of the second fan assembly so that the flow is oriented in apredetermined direction with respect to the inlet face of the second fanassembly; and one or more heat pipes coupled to the at least one finarray between the first face and the second face, wherein the heat pipesare configured to draw heat from the flow of air that flows through theheat exchanger.